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CVE-2020-26263

Published: 21 December 2020

tlslite-ng is an open source python library that implements SSL and TLS cryptographic protocols. In tlslite-ng before versions 0.7.6 and 0.8.0-alpha39, the code that performs decryption and padding check in RSA PKCS#1 v1.5 decryption is data dependant. In particular, the code has multiple ways in which it leaks information about the decrypted ciphertext. It aborts as soon as the plaintext doesn't start with 0x00, 0x02. All TLS servers that enable RSA key exchange as well as applications that use the RSA decryption API directly are vulnerable. This is patched in versions 0.7.6 and 0.8.0-alpha39. Note: the patches depend on Python processing the individual bytes in side-channel free manner, this is known to not the case (see reference). As such, users that require side-channel resistance are recommended to use different TLS implementations, as stated in the security policy of tlslite-ng.

Priority

Medium

Cvss 3 Severity Score

7.5

Score breakdown

Status

Package Release Status
tlslite-ng
Launchpad, Ubuntu, Debian
bionic Needs triage

focal Does not exist

groovy Does not exist

hirsute Does not exist

impish Does not exist

jammy Does not exist

kinetic Does not exist

lunar Does not exist

mantic Does not exist

trusty Does not exist

upstream Needs triage

xenial Needs triage

Severity score breakdown

Parameter Value
Base score 7.5
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact None
Availability impact None
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N